A/C Compressor Zener Diode to stop radio popping

[Kenneth Keith]

Hey Listers,

Does anyone know where I can find the appropriate Zener Diode to use
with the a/c compressor (patient is a 200q20v) to stop the feedback
popping when the clutch cycles?  I found some on Mouser.com but they
are sold by large quantities and I just need one.
http://www.sjmautotechnik.com says it needs to be one with an 18v
breakdown voltage.

Has anyone done the mod?  It's described here:
http://www.sjmautotechnik.com/trouble_shooting/elec.html#click

Cheers,

Kenneth